import pandas as pd
df = pd.read_excel('data.xlsx')

x = df['监测点名称'].values.tolist()
print(len(x),x)

df2 = pd.read_excel('data_ld.xlsx')

y = df2['监测点名称'].values.tolist()
print(len(y),y)

for i in x:
    if i not in y:
        print(i)